The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An aircraft is generally moved by several turbojet engines each housed in a nacelle accommodating a set of auxiliary actuating devices relating to its operation and providing various functions when the turbojet engine is in operation or shut-down.
These auxiliary actuating devices comprise in particular a thrust reverser device.
A turbojet engine nacelle generally has a substantially tubular structure comprising an air inlet upstream of the turbojet engine, a mid-section intended to surround a fan of said turbojet engine, a downstream section intended to surround the combustion chamber of the turbojet engine and possibly integrating thrust reverser means, and is generally terminated by an ejection nozzle whose outlet is located downstream of the turbojet engine.
The modern nacelles are intended to accommodate a bypass turbojet engine capable of generating, via the blades of the rotating fan, a hot air flow (primary flow) and a cold air flow (secondary flow) which circulates outside the turbojet engine through an annular passage, also called flow path, formed between a fairing of the turbojet engine and an inner wall of the nacelle. The two air flows are ejected from the turbojet engine by the backside of the nacelle.
The downstream section of a nacelle for such a turbojet engine generally has an Outer Fixed Structure (OFS) and a concentric Inner Fixed Structure (IFS), surrounding a downstream section of the turbojet engine accommodating the gas generator of the turbojet engine.
The inner and outer fixed structures define the flow path intended to channel the cold air flow which circulates outside the turbojet engine.
The role of a thrust reverser, during the landing of an aircraft, is to improve the braking capability of said aircraft by redirecting forwards at least one part of the air ejected from the turbojet engine. In this phase, the thrust reverser obstructs at least one part of the flow path of the cold flow and directs this flow forwardly of the nacelle, thereby generating a counter-thrust which is added to the braking of the wheels and air brakes of the airplane.
In general, the structure of a thrust reverser comprises a cowl which is movably mounted in longitudinal translation from forth to back along a direction substantially parallel to the axis of the nacelle, between a closing position in which the cowl provides the aerodynamic continuity of the nacelle, and an opening position in which the cowl opens a passage in the nacelle.
In the case of a thrust reverser with cascade vanes, the reorientation of the air flow is performed by cascade vanes, associated to thrust reverser flaps blocking at least partially the air circulation flow path, the cowl having only a simple sliding function aiming to uncover or cover these cascade vanes.
The thrust reverser flaps, also called blocking flaps, for their part, are activated and driven by the sliding of the movable cowl until at least partially obstructing the flow path downstream of the cascades, so as to improve the reorientation of the cold air flow.
Nacelles called nacelles with O-shaped structure are known, known under the terminology “O-Duct”, which have a downstream structure having a substantially peripheral single structure extending from one side of the reactor mast to the other side.
It follows that such a structure generally has a substantially peripheral single cowl which, for maintenance purposes, opens by downstream translation along the longitudinal axis of the nacelle.
For a detailed description, reference might be made to the documents FR 2 911 372 and FR 2 952 681.
Moreover, the O-duct nacelles include cascade vanes which are movably mounted in translation and capable of being retracted at least partially in the thickness of the mid-section of the nacelle and thereby overlapping the fan casing when the thrust reverser is inactive, in the direct jet position. In the thrust reversal position, the cascade vanes are displaced with the movable cowl.
In the case of a thrust reverser for an O-duct nacelle, the mast may be equipped with rails allowing the sliding of the movable cowl and the cascades.
On modern propulsion units of large dimensions and having structures of great flexibility, this configuration may induce significant stresses in the structure of the thrust reverser.
A thrust reverser device described in the document FR-A-3002785 is also known, which includes rails which are arranged on either side of the mast and which provide the sliding of the movable cowl and the cascade vanes.
This type of device has drawbacks in particular in that in case of relative displacement of the turbojet engine relative to the mast, the movable cascades, which are fastened on the mast, are likely to be subjected to torsion forces.
Indeed, in order to limit the volume of modern nacelles, in particular the radial section of the nacelles, the section of the movable cascades is limited in order to reduce their bulk, so that the inertia of the cascades and the mechanical resistance oppose thereby is reduced.
Furthermore, there is also a risk of relative displacement of the rails therebetween and of the significant geometrical variations which risk compromising the proper operation of the kinematics of the thrust reverser.
Finally, the mounting/dismounting of the propulsion unit implies dismounting all or part of the thrust reverser.